Flat drop cable

ABSTRACT

An example fiber optic cable includes an outer jacket having an elongated transverse cross-sectional profile defining a major axis and a minor axis. The transverse cross-sectional profile has a maximum width that extends along the major axis and a maximum thickness that extends along the minor axis. The maximum width of the transverse cross-sectional profile is longer than the maximum thickness of the transverse cross-sectional profile. The outer jacket also defines first and second separate passages that extend through the outer jacket along a lengthwise axis of the outer jacket. The second passage has a transverse cross-sectional profile that is elongated in an orientation extending along the major axis of the outer jacket. The fiber optic cable also includes a plurality of optical fibers positioned within the first passage a tensile strength member positioned within the second passage.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 13/246,225,filed Sep. 27, 2011, now U.S. Pat. No. 8,290,320, which is acontinuation of application Ser. No. 12/607,748, filed Oct. 28, 2009,now U.S. Pat. No. 8,041,166, which claims the benefit of provisionalapplication Ser. No. 61/109,041, filed Oct. 28, 2008, which applicationsare incorporated herein by reference in their entirety.

BACKGROUND

A fiber optic cable typically includes: (1) an optical fiber; (2) abuffer layer that surrounds the optical fiber; (3) a plurality ofreinforcing members loosely surrounding the buffer layer; and (4) anouter jacket. Optical fibers function to carry optical signals. Atypical optical fiber includes an inner core surrounded by a claddingthat is protected by a coating. The buffer layer functions to surroundand protect the coated optical fibers. Reinforcing members addmechanical reinforcement to fiber optic cables to protect the internaloptical fibers against stresses applied to the cables duringinstallation and thereafter. Outer jackets also provide protectionagainst chemical damage.

Drop cables used in fiber optic networks can be constructed having ajacket with a flat transverse profile. Such cables typically include acentral buffer tube containing a plurality of optical fibers, andreinforcing members such as rods made of glass reinforced epoxy embeddedin the jacket on opposite sides of the buffer tube. U.S. Pat. No.6,542,674 discloses a drop cable of a type described above. Flat dropcables of the type described above are designed to be quite robust.However, as a result of such cables being strong and robust, such cablesare typically quite stiff, inflexible and difficult to handle.Additionally, such cables can be expensive to manufacture.

SUMMARY

The present disclosure relates to a fiber optic cable including an outerjacket having an elongated transverse cross-sectional profile defining amajor axis and a minor axis. The transverse cross-sectional profile hasa maximum width that extends along the major axis and a maximumthickness that extends along the minor axis. The maximum width of thetransverse cross-sectional profile is longer than the maximum thicknessof the transverse cross-sectional profile. The outer jacket also definesfirst and second separate passages that extend through the outer jacketalong a lengthwise axis of the outer jacket. The second passage has atransverse cross-sectional profile that is elongated in an orientationextending along the major axis of the outer jacket. The fiber opticcable also includes a plurality of optical fibers positioned within thefirst passage a tensile strength member positioned within the secondpassage. The tensile strength member has a highly flexible constructionand a transverse cross-sectional profile that is elongated in theorientation extending along the major axis.

A variety of additional aspects will be set forth in the descriptionthat follows. These aspects can relate to individual features and tocombinations of features. It is to be understood that both the foregoinggeneral description and the following detailed description are exemplaryand explanatory only and are not restricted of the broad concepts uponwhich the embodiments disclosed herein are based.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a transverse cross-sectional view of a fiber optic cablehaving features that are examples of aspects in accordance with theprinciples of the present disclosure.

FIG. 2 is a perspective view of an optical fiber suitable for use in thefiber optic cable of FIG. 1.

FIG. 3 is a transverse cross-sectional view of another fiber optic cablehaving features that are examples of aspects in accordance with theprinciples of the present disclosure.

FIG. 4 is a plan view of another fiber optic cable in accordance withthe principles of the present disclosure.

FIG. 5 is a transverse cross-sectional view of the fiber optic cable ofFIG. 4 taken along section line 5-5.

FIG. 6 is a perspective view of contrahelical separating members thatcan be used to group together the optical fibers of the fiber opticcable of FIGS. 4 and 5 and can also be used to separate the opticalfibers from the cable jacket material enclosing the fibers.

FIG. 7 is a plan view of a further fiber optic cable in accordance withthe principles of the present disclosure.

FIG. 8 is a transverse cross-sectional view of the fiber optic cable ofFIG. 7 taken along section line 8-8.

FIG. 9 is an end view of a test system for testing the flexibility ofthe strength members of the fiber optic cables of FIGS. 4, 5, 7 and 8.

FIG. 10 is a top view of the test system of FIG. 9.

FIG. 11 is a top plan view of still another fiber optic cable inaccordance with the principles of the present disclosure.

FIG. 12 is a transverse cross-sectional view of the fiber optic cable ofFIG. 11 taken along section line 12-12.

DETAILED DESCRIPTION

FIG. 1 shows a fiber optic cable 10 in accordance with the principles ofthe present disclosure. The fiber optic cable 10 includes at least oneoptical fiber 12 contained within a buffer tube 14. An outer jacket 16surrounds the buffer tube 14. A reinforcing member 18 is embedded in theouter jacket 16 to provide the fiber optic cable 10 with axialreinforcement.

Referring still to FIG. 1, the outer jacket 16 has a non-circular outerprofile. For example, as shown at FIG. 1, when viewed in transversecross-section, the outer profile of the outer jacket 16 has a flatgenerally obround or rectangular shape. The outer jacket 16 is longeralong a major axis 20 than along a minor axis 21. The major and minoraxes 20, 21 are perpendicular to one another and intersect at a center27 of the outer jacket 16.

Referring still to FIG. 1, the outer jacket 16 defines a single fiberpassage 23 in which the buffer tube 14 is located. As illustrated in theexample of FIG. 1, the fiber passage 23 may have a circular profile. Thefiber passage 23 has a center 25 that is offset from the center 27 ofthe outer jacket 16.

The outer jacket 16 also defines a single reinforcing member passage 28having a center 30 that is also offset from the center 27 of the outerjacket 16. The center 27 of the outer jacket 16 is the geometric centerof the outer profile of the outer jacket 16. As illustrated in theexample of FIG. 1, the reinforcing member passage 28 may have a circularprofile. The center 25 of the fiber passage 23 is located at an oppositeside of the minor axis 21 as compared to the center 30 of thereinforcing member passage 28. Consequently, the outer jacket 16 isthicker along the minor axis 21 through the center 27 of the outerjacket 16 than along an axis parallel to the minor axis 21 through thecenter 25 of the fiber passage 23 or an axis parallel to the minor axis21 through the center 30 of the reinforcing member passage 28.

Furthermore, because the center 25 of the fiber passage 23 is located atan opposite side of the minor axis 21 as compared to the center 30 ofthe reinforcing member passage 28, the outer jacket 16 contains nocavities along the minor axis 21 through the center 27 of the outerjacket 16. Because the outer jacket 16 contains no cavities along theminor axis 21 through the center 27 of the outer jacket 16, the outerjacket 16 does not significantly compress the fiber passage 23 or crushthe optical fibers 12 when the fiber optic cable 10 is clamped duringinstallation of the fiber optic cable 10. Rather, the portion of theouter jacket 16 along the minor axis 21 through the center 27 of theouter jacket 16 serves to support the fiber passage 23 againstcompression forces exerted by clamping during installation.

It will be appreciated that the outer jacket 16 can be made of anynumber of different types of polymeric materials. In one embodiment, theouter jacket 16 is made of a medium density ultra-high molecular weightpolyethylene.

The buffer tube 14 can also be made of any number of different polymericmaterials. For example, the buffer tube 14 can be made of a polymericmaterial such as polyvinyl chloride (PVC). Other polymeric materials(e.g., polyethylenes, polyurethanes, polypropylenes, polyvinylidenefluorides, ethylene vinyl acetate, nylon, polyester, or other materials)may also be used.

In certain embodiments, the reinforcing member 18 can include a singlereinforcing rod positioned within the reinforcing member passage 28 ofthe outer jacket 16. In certain embodiments, the single rod can be madeof glass fibers imbedded within a resin such as epoxy.

Referring now to FIGS. 1 and 2, one or more optical fibers 12 can bepositioned within the buffer tube 14. In a preferred embodiment, thebuffer tube 14 contains at least twelve optical fibers 12. It will beappreciated that the optical fibers 12 can have any number of differenttypes of configurations. In one embodiment, the optical fiber 12includes a core 32. The core 32 is made of a glass material, such as asilica-based material, having an index of refraction. In the subjectembodiment, the core 32 has an outer diameter D₁ of less than or equalto about 10 μm.

The core 32 of each optical fiber 12 is surrounded by a first claddinglayer 34 that is also made of a glass material, such as a silicabased-material. The first cladding layer 34 has an index of refractionthat is less than the index of refraction of the core 32. Thisdifference between the index of refraction of the first cladding layer34 and the index of refraction of the core 32 allows an optical signalthat is transmitted through the optical fiber 12 to be confined to thecore 32.

A trench layer 36 surrounds the first cladding layer 34. The trenchlayer 36 has an index of refraction that is less than the index ofrefraction of the first cladding layer 34. In the subject embodiment,the trench layer 36 is immediately adjacent to the first cladding layer34.

A second cladding layer 38 surrounds the trench layer 36. The secondcladding layer 38 has an index of refraction. In the subject embodiment,the index of refraction of the second cladding layer 38 is about equalto the index of refraction of the first cladding layer 34. The secondcladding layer 38 is immediately adjacent to the trench layer 36. In thesubject embodiment, the second cladding layer 38 has an outer diameterD₂ of less than or equal to 125 μm.

A coating, generally designated 40, surrounds the second cladding layer38. The coating 40 includes an inner layer 42 and an outer layer 44. Inthe subject embodiment, the inner layer 42 of the coating 40 isimmediately adjacent to the second cladding layer 38 such that the innerlayer 42 surrounds the second cladding layer 38. The inner layer 42 is apolymeric material (e.g., polyvinyl chloride, polyethylenes,polyurethanes, polypropylenes, polyvinylidene fluorides, ethylene vinylacetate, nylon, polyester, or other materials) having a low modulus ofelasticity. The low modulus of elasticity of the inner layer 42functions to protect the optical fiber 12 from microbending.

The outer layer 44 of the coating 40 is a polymeric material having ahigher modulus of elasticity than the inner layer 42. In the subjectembodiment, the outer layer 44 of the coating 40 is immediately adjacentto the inner layer 42 such that the outer layer 44 surrounds the innerlayer 42. The higher modulus of elasticity of the outer layer 44functions to mechanically protect and retain the shape of optical fiber12 during handling. In the subject embodiment, the outer layer 44defines an outer diameter D₃ of less than or equal to 500 μm. In anotherembodiment, the outer layer 44 has an outer diameter D₃ of less than orequal to 250 μm.

In the subject embodiment, the optical fiber 12 is manufactured toreduce the sensitivity of the optical fiber 12 to micro or macro-bending(hereinafter referred to as “bend-insensitive”). An exemplary bendinsensitive optical fiber has been described in U.S. Pat. ApplicationPublication Nos. 2007/0127878 and 2007/0280615 that are herebyincorporated by reference in their entirety. An exemplarybend-insensitive optical fiber is commercially available from DrakaComteq under the name BendBright XS.

Because the fiber optic cable 10 is reinforced by a single reinforcingmember 18 that is offset from the center 27 of the outer jacket 16, thefiber optic cable 10 is provided with an asymmetric reinforcingconfiguration.

FIG. 3 shows another fiber optic cable 10′ in accordance with theprinciples of the present disclosure. The fiber optic cable 10′ has thesame construction as the fiber optic cable 10 except the buffer tube 14has been eliminated. In this design, the optical fibers 12 arepositioned directly within the fiber passage 23 of the outer jacket 16without any intermediate buffer tubes. In this manner, the portion ofthe outer jacket 16 defining the fiber passage 23 functions as a buffertube for containing the optical fibers.

It will be appreciated that the cables of FIGS. 1 and 3 can be used asdrop cables in a fiber optic network. For example, the fiber opticcables 10, 10′ can be used as drop cables in fiber optic networks suchas the networks disclosed in U.S. Provisional Patent Application Ser.No. 61/098,494, entitled “Methods and Systems for Distributing FiberOptic Telecommunications Services to a Local Area,” filed on Sep. 19,2008 and hereby incorporated by reference in its entirety.

FIGS. 4 and 5 depict another fiber optic cable 100 in accordance withthe principles of the present disclosure. Generally, the cable 100includes an outer jacket 102 defining first and second generallyparallel passages 104, 106. The cable 100 also includes a plurality ofbend insensitive fibers 12 positioned within the first passage 104 and astrength member 107 (i.e., a tensile reinforcing member) positionedwithin the second passage 106. Such a construction allows the cable 100to be readily used for applications in which drop cables are normallyused and also allows the cable 100 to be wrapped around a cable storagespool having a relatively small diameter without damaging the cable 100.

Referring to FIG. 5, the cable 100 has an elongated transversecross-sectional profile (e.g., a flattened cross-sectional profile, anoblong cross-sectional profile, an obround cross-sectional profile,etc.) defined by the outer jacket 102. The cable 100 defines a majoraxis 108 and a minor axis 110. A width W1 of the outer jacket 102extends along the major axis 108 and a thickness T1 of the outer jacket102 extends along the minor axis 110. The width W1 is longer than thethickness T1. In certain embodiments, the width W1 is at least 50%longer than the thickness. As depicted in FIG. 5, the width W1 is amaximum width of the outer jacket 102 and the thickness T1 is a maximumthickness of the outer jacket 102.

In the depicted embodiment of FIG. 5, the transverse cross-sectionalprofile defined by the outer jacket 102 of FIG. 5 is generallyrectangular with rounded ends. The major axis 108 and the minor axis 110intersect perpendicularly at a lengthwise axis 112 of the cable 100.

The construction of the cable 100 allows the cable 100 to be bent moreeasily along a plane P1 that coincides with the minor axis 110 thanalong a plane P2 that coincides with the major axis 108. Thus, when thecable 100 is wrapped around a spool or guide, the cable 100 ispreferably bent along the plane P1.

As indicated above, the outer jacket 102 defines the elongate transversecross-sectional profile of the cable 100. The first and second passages104, 106 are aligned along the major axis 108 of the cable 100. Thefirst passage 104 has a generally circular transverse cross-sectionalprofile while the second passage 106 has an elongate transversecross-sectional profile. For example, the second passage 106 iselongated in an orientation that extends along the major axis 108 of thecable 100. In the depicted embodiment, the first passage 104 is notlined with a buffer tube. However, in other embodiments, a buffer tubemay be used.

It will be appreciated that the outer jacket 102 of the cable 100 can beshaped through an extrusion process and can be made by any number ofdifferent types of polymeric materials. In certain embodiments, theouter jacket 102 can have a construction the resists post-extrusionshrinkage of the outer jacket 102. For example, the outer jacket 102 caninclude a shrinkage reduction material disposed within a polymeric basematerial (e.g., polyethylene). U.S. Pat. No. 7,379,642, which is herebyincorporated by reference in its entirety, describes an exemplary use ofshrinkage reduction material within the base material of a fiber opticcable jacket.

In one embodiment, the shrinkage reduction material is a liquid crystalpolymer (LCP). Examples of liquid crystal polymers suitable for use infiber-optic cables are described in U.S. Pat. Nos. 3,911,041; 4,067,852;4,083,829; 4,130,545; 4,161,470; 4,318,842; and 4,468,364 which arehereby incorporated by reference in their entireties. To promoteflexibility of the cable 100, the concentration of shrinkage material(e.g. LCP) is relatively small as compared to the base material. In oneembodiment, and by way of example only, the shrinkage reduction materialconstitutes less than about 10% of the total weight of the outer jacket102. In another embodiment, and by way of example only, the shrinkagereduction material constitutes less than about 5% of the total weight ofthe outer jacket 102. In another embodiment, the shrinkage reductionmaterial constitutes less than about 2% of the total weight of the outerjacket 102. In another embodiment, shrinkage reduction materialconstitutes less than about 1.9%, less than about 1.8%, less than 1.7%,less than about 1.6%, less than about 1.5%, less than about 1.4%, lessthan about 1.3%, less than about 1.2%, less than about 1.1%, or lessthan about 1.0% of the total weight of the outer jacket 102.

Example base materials for the outer jacket 102 include low-smoke zerohalogen materials such as low-smoke zero halogen polyolefin andpolycarbon. In other embodiments, the base material can include thermalplastic materials such as polyethylene, polypropylene,ethylene-propylene, copolymers, polystyrene and styrene copolymers,polyvinyl chloride, polyamide (nylon), polyesters such as polyethyleneterephthalate, polyetheretherketone, polyphenylene sulfide,polyetherimide, polybutylene terephthalate, as well as other plasticmaterials. In still other embodiments, the outer jacket 102 can be madeof low density, medium density or high density polyethylene materials.Such polyethylene materials can include low density, medium density orhigh density ultra-high molecular weight polyethylene materials.

The first passage 104 of the outer jacket 102 is sized to receive one ormore of the bend insensitive fibers 12. The bend insensitive fibers arepreferably unbuffered and in certain embodiments have outer diameters inthe range of 230-270 μm. In one embodiment, the first passage 104 issized to receive at least 12 of the bend insensitive fibers 12. When thefibers 12 are positioned within the first passage 104, it is preferredfor the fibers 12 to occupy less than 60% of the total transversecross-sectional area defined by the first passage 104.

It is preferred for the first passage 104 to be dry and not to be filledwith a water-blocking gel. Instead, to prevent water from migratingalong the first passage 104, structures such water-swellable fibers,water-swellable tape, or water-swellable yarn can be provided within thepassage 104 along with the fibers 12. However, in certain embodimentswater-blocking gel may be used.

The strength member 107 of the cable 100 preferably has a transversecross-sectional profile that matches the transverse cross-sectionalprofile of the second passage 106. As shown at FIG. 5, the strengthmember 107 has a transverse cross-sectional width W2 that is greaterthan a transverse cross-sectional thickness T2 of the strength member107. The width W2 extends along the major axis 108 of the cable whilethe thickness T2 extends along the minor axis 110 of the cable 100. Inthe depicted embodiment, the thickness T2 is bisected by the major axis108. In certain embodiments, the width W2 of the strength member 107 isat least 50% longer than the thickness T2, or the width W2 of thestrength member 107 is at least 75% longer than the thickness T2, or thewidth W2 of the strength member 107 is at least 100% longer than thethickness T2, or the width W2 of the strength member 107 is at least200% longer than the thickness T2, or the width W2 of the strengthmember 107 is at least 300% longer than the thickness T2, or the widthW2 of the strength member 107 is at least 400% longer than the thicknessT2. As depicted in FIG. 5, the width W2 is a maximum width of thestrength member 107 and the thickness T2 is a maximum thickness of thestrength member 107.

In certain embodiments, the strength member 107 is bonded to the outerjacket 102. The bonding between the strength member 107 and the outerjacket 102 can be chemical bonding or thermal bonding. In oneembodiment, the strength member 107 may be coated with or otherwiseprovided with a material having bonding characteristics (e.g., ethyleneacetate) to bond the strength member 107 to the outer jacket 102.

The strength member 107 preferably has a construction that is highlyflexible and highly strong in tension. For example, in certainembodiments, the strength member 107 provides the vast majority of thetensile load capacity of the cable 100. For example, in one embodiment,the strength member 107 carries at least 95% of a 150 pound tensile loadapplied to the cable 100 in a direction along the lengthwise axis 112.In one embodiment, the strength member 107 can carry a 150 pound tensileload applied in an orientation extending along a central longitudinalaxis of the strength member 107 without undergoing meaningfuldeterioration of the tensile properties of the strength member 107. Inanother embodiment, the strength member 107 can carry a 200 poundtensile load applied in an orientation extending along the centrallongitudinal axis of the strength member 107 without undergoingmeaningful deterioration in its tensile properties. In still anotherembodiment, the strength member 107 can carry a 300 pound tensile loadapplied in an orientation that extends along the central longitudinalaxis of the strength member 107 without experiencing meaningfuldeterioration of its tensile properties.

It is preferred for the strength member 107 to be able to provide thetensile strengths described above while concurrently being highlyflexible. In determining the tensile strength of the cable 102, tensileload is applied to the cable 102 in a direction that extends along thelengthwise axis 112 of the cable 100. Similarly, to determine thetensile strength of the strength member 107, tensile load is applied tothe strength member 107 in a direction that extends along centrallongitudinal axis 114 of the strength member 107. In one embodiment, astrength member 107 having tensile strength characteristics as describedabove also has a flexibility that allows the strength member 107 to bewrapped at least 360 degrees around a mandrel 300 (see FIGS. 9 and 10)having a 10 millimeter outer diameter for one hour withoutundergoing/experiencing meaningful deterioration/degradation of thetensile strength properties of the strength member 107. As shown atFIGS. 9 and 10, the 360 degree wrap is aligned generally along a singleplane P3 (i.e., the 360 degree wrap does not form a helix having anextended axial length). In this way, the strength member 107 conforms tothe outer diameter of the mandrel and generally forms a circle having aninner diameter of 10 millimeters. This test can be referred to as the“mandrel wrap” test. In certain embodiments, the strength member 107maintains at least 95% of its pre-mandrel wrap test tensile strengthafter having been subjected to the mandrel wrap test. In certainembodiments, the strength member 107 does not “broom stick” whensubjected to the mandrel wrap test described. As used herein, the term“broom stick” means to have reinforcing elements of the strength membervisually separate from the main body of the strength member 107. Incertain embodiments, the strength member 107 does not generate anyaudible cracking when exposed to the mandrel wrap test.

In certain embodiments, the strength member 107 is formed by a generallyflat layer of reinforcing elements (e.g., fibers or yarns such as aramidfibers or yarns) embedded or otherwise integrated within a binder toform a flat reinforcing structure (e.g., a structure such as asheet-like structure, a film-like structure, or a tape-like structure).In one example embodiment, the binder is a polymeric material suchethylene acetate acrylite (e.g., UV-cured, etc.), silicon (e.g., RTV,etc.), polyester films (e.g., biaxially oriented polyethyleneterephthalate polyester film, etc.), and polyisobutylene. In otherexample instances, the binder may be a matrix material, an adhesivematerial, a finish material, or another type of material that binds,couples or otherwise mechanically links together reinforcing elements.

In other embodiments, the strength member 107 can have a glassreinforced polymer (GRP) construction. The glass reinforced polymer caninclude a polymer base material reinforced by a plurality of glassfibers such as E-glass, S-glass or other types of glass fiber. Thepolymer used in the glass reinforced polymer is preferably relativelysoft and flexible after curing. For example, in one embodiment, thepolymer has a Shore A hardness less than 50 after curing. In otherembodiments, the polymer has a Shore A hardness less than 46 aftercuring. In certain other embodiments, the polymer has a Shore A hardnessin the range of about 34-46.

In one embodiment, the strength member 107 can have a width of about0.085 inches and a thickness of about 0.045 inches. In anotherembodiment, such a strength member may have a width of about 0.125inches and a thickness of about 0.030 inches. In still furtherembodiments, the strength member has a thickness in the range of0.020-0.040 inches, or in the range of 0.010-0.040 inches, or in therange of 0.025-0.035 inches. Of course, other dimensions could be usedas well. In additional embodiments, the strength member may have a widthin the range of 0.070-0.150 inches. Of course, other sizes could be usedas well.

In certain embodiments, the strength member 107 preferably does notprovide the cable 100 with meaningful resistance to compression loadingin an orientation extending along the lengthwise axis 112. For example,in certain embodiments, the outer jacket 102 provides greater resistanceto compression than the strength member 107 in an orientation extendingalong the lengthwise axis 112. Thus, in certain embodiments, thereinforcing member 107 does not provide the cable 100 with meaningfulcompressive reinforcement in an orientation that extends along thelengthwise axis 112. Rather, resistance to shrinkage or othercompression of the cable 100 along the lengthwise axis 112 can beprovided by the outer jacket 102 itself through the provision of theshrinkage reduction material within the base material of the outerjacket 102. In this type of embodiment, when a compressive load isapplied to the cable 100 along the lengthwise axis 112, a vast majorityof the compressive load will be carried by the outer jacket 102 ascompared to the strength member 107.

As depicted in FIG. 5, the fibers 12 are loose within the first passage104. In other embodiments, the fibers 12 within the first passage 104can be surrounded and grouped together by separating members that canseparate the fibers 12 from the jacket material defining the firstpassage 104. Such separating can assist in preventing the fibers 12 fromcontacting the extrusion die or extrusion tip during extrusion of theouter jacket 102 over the fibers 12. In certain embodiments, first andsecond sets of separating members 120 a, 120 b can be contra-helicallyserved about the group of fibers 12. For example, in the depictedembodiment of FIG. 6, the first set of separating members 120 a isdisposed about the fibers 12 in a generally right-handed helical wrapconfiguration while the second set of separating members 120 b isdisposed about the optical fibers 12 in a generally left-handed helicalwrap configuration. In certain embodiments, the separating members 120a, 120 b can have helical wrap angles a less than 20 degrees or lessthan 15 degrees. In certain embodiments, the separating members can beyarns. In one embodiment, the separating members are formed by aramidyarn. In certain embodiments, water swellable material can be coated onor otherwise incorporated into the binding members.

In the depicted embodiment of FIG. 6, the contra-helical serve ofseparating members extends around the entire group of optical fibers 12.In other embodiments, contra-helical serving can be used to divide thefibers 12 into separate groups. For example, the fibers 12 can beseparated into three groups of 4 optical fibers 12 with contra-helicalserving provided around each of the groups of 4 fibers 12.

FIGS. 7 and 8 depict another cable 200 in accordance with the principlesof the present disclosure. The cable 200 includes many of the samecomponents as the as the cable 100 (e.g., the strength member 107, theoptical fibers 12, the passages 104, 106). However, the cable 200includes an outer jacket 202 having a transverse cross-sectional profilethat has been modified to include a variable thickness (e.g., a dualthickness) to improve the crush-resistance of the cable 200. Crushresistance can be significant when the cable is used with a cable clampsuch as a “P-clamp.”

Referring to FIG. 8, the outer jacket 202 of the cable 200 has anelongated transverse cross-sectional profile. The cable 200 defines amajor axis 208 and a minor axis 210. A width W3 of the outer jacket 202extends along the major axis 208 and thicknesses T3, T4 of the outerjacket 202 extend along the minor axis 210. The thickness T3 is smallerthan the thickness T4, and the width W3 is greater than the thicknessT4. The thickness T3 is defined by a first portion 230 of the jacket 202in which the first passage 104 containing the optical fibers 12 isformed. The thickness T4 is defined by a second portion 232 of thejacket 202 in which the second passage 106 containing the strengthmember 107 is formed. In the depicted embodiment, the first portion 230is positioned at or defines a first end 234 of the transversecross-sectional profile of the cable 200 and the second portion 231 ispositioned at or defines an opposite second end 236 of the transversecross-sectional profile of the cable 200. When viewed in transversecross-section, the thickness T3 coincides with a center of the firstpassage 104 and the thickness T4 coincides with a center of the secondpassage 106. When the cable 200 is compressed in an orientation thatextends along the minor axis 210 (e.g., with a cable clamp), theincreased thickness T4 provided by the second portion 232 of the jacket202 carries most of the compressive load thereby preventing the firstpassage 104 from being deformed. In this way, the fibers 12 within thefirst passage 104 are prevented from being damaged by the compressiveaction.

While most of the drawings of the present disclosure show cables havingasymmetrical reinforcing configurations in which strength members areprovided only on one side of a passage containing optical fibers, itwill be appreciated that aspects of the present disclosure can be usefor other cables as well. For example, aspects of the present disclosurecan be used for a flat drop cable 400 (see FIGS. 11 and 12) having acentral passage 404 for containing fibers 12 and two passages 406 onopposite sides of the central passage 404 for containing strengthmembers 107.

The above specification provides examples of how certain inventiveaspects may be put into practice. It will be appreciated that theinventive aspects can be practiced in other ways than those specificallyshown and described herein without departing from the spirit and scopeof the inventive aspects of the present disclosure.

What is claimed is:
 1. A fiber optic cable comprising: an outer jackethaving an elongated transverse cross-sectional profile defining a majoraxis and a minor axis, the transverse cross-sectional profile having amaximum width that extends along the major axis and a maximum thicknessthat extends along the minor axis, the maximum width of the transversecross-sectional profile being longer than the maximum thickness of thetransverse cross-sectional profile, the outer jacket also defining firstand second separate passages that extend through the outer jacket alonga lengthwise axis of the outer jacket, the second passage having atransverse cross-sectional profile that is elongated in an orientationextending along the major axis of the outer jacket; at least one opticalfiber positioned within the first passage; and a tensile strength memberpositioned within the second passage, the tensile strength member havinga transverse cross-sectional profile that is elongated in theorientation extending along the major axis, the tensile strength memberbeing sufficiently flexible to be wrapped in a circle having a 10millimeter inner diameter for one hour without undergoing meaningfuldeterioration in tensile strength.
 2. The fiber optic cable of claim 1,wherein the first passage has a generally round transversecross-sectional profile.
 3. The fiber optic cable of claim 1, whereinthe first passage is not lined with a buffer tube.
 4. The fiber opticcable of claim 3, wherein two separating members are contrahelicallyserved about the optical fibers to separate the optical fibers from aportion of the outer jacket that defines the first passage.
 5. The fiberoptic cable of claim 1, wherein the strength member is bonded to theouter jacket.
 6. The fiber optic cable of claim 5, wherein the strengthmember is bonded to the outer jacket with an adhesive material.
 7. Thefiber optic cable of claim 6, wherein the adhesive material includesethylene acetate.
 8. The fiber optic cable of claim 1, wherein theoptical fibers include bend insensitive optical fibers.
 9. The fiberoptic cable of claim 1, wherein the first and second passages arealigned along the major axis.
 10. The fiber optic cable of claim 9,wherein the tensile strength member provides asymmetrical tensilereinforcement to the fiber optic cable about the minor axis.
 11. Thefiber optic cable of claim 1, wherein the tensile strength memberprovides less compressive reinforcement than the outer jacket in anorientation that extends along the lengthwise axis.
 12. The fiber opticcable of claim 1, wherein the tensile strength member can carry atensile load of at least 300 pounds.
 13. The fiber optic cable of claim1, wherein the tensile strength member can carry a tensile load of atleast 150 pounds.
 14. The fiber optic cable of claim 12, wherein thetensile strength member retains at least 95 percent of its pre-wrappedtensile strength after having been wrapped in the circle having the 10millimeter inner diameter for one hour.
 15. The fiber optic cable ofclaim 13, wherein the tensile strength member retains at least 95percent of its pre-wrapped tensile strength after having been wrapped inthe circle having the 10 millimeter inner diameter for one hour.
 16. Thefiber optic cable of claim 1, wherein the outer jacket includes apolymeric base material and a shrinkage reduction material disposedwithin the polymeric base material.
 17. The fiber optic cable of claim16, wherein the shrinkage reduction material includes a liquid crystalpolymer.
 18. The fiber optic cable of claim 1, wherein the first andsecond passages are aligned along the major axis, wherein the firstpassage has a circular transverse cross-sectional profile, wherein thefirst passage is not lined with a buffer tube, wherein the tensilestrength member is bonded to the outer jacket, and wherein the outerjacket includes a polymeric base material and a liquid crystal polymerdisposed within the base material.
 19. The fiber optic cable of claim 1,wherein when the outer jacket is viewed in transverse cross-section, theouter jacket has a first portion in which the first passage is definedand a second portion in which the second passage is defined, wherein thefirst portion defines a first thickness and the second portion defines asecond thickness, wherein the second thickness is the maximum thicknessof the outer jacket, and wherein the second thickness is thicker thanthe first thickness.
 20. The fiber optic cable of claim 19, wherein thefirst thickness coincides with a center of the first passage and thesecond thickness coincides with a center of the second passage.
 21. Afiber optic cable comprising: an outer jacket having an elongatedtransverse cross-sectional profile defining a major axis and a minoraxis, the transverse cross-sectional profile having a maximum width thatextends along the major axis and a maximum thickness that extends alongthe minor axis, the maximum width of the transverse cross-sectionalprofile being longer than the maximum thickness of the transversecross-sectional profile, the outer jacket also defining first and secondseparate passages that extend through the outer jacket along alengthwise axis of the outer jacket, the second passage having atransverse cross-sectional profile that is elongated in an orientationextending along the major axis of the outer jacket; at least one opticalfiber positioned within the first passage; and a tensile strength memberpositioned within the second passage, the tensile strength member havinga transverse cross-sectional profile that is elongated in theorientation extending along the major axis, the tensile strength memberprovides less compressive reinforcement than the outer jacket in anorientation that extends along the lengthwise axis.